Recently, introduction of touch panel systems to various kinds of electronic devices has been growing rapidly. For example, the touch panel systems are introduced to portable information devices such as smartphones and automatic vending machines such as automatic ticket machines.
The touch panel system is typically configured to include (i) a display device and (ii) a touch panel stacked on an upper side (front surface) of the display device. Therefore, a sensor provided on the touch panel is likely to be affected not only by a noise such as a clock generated in the display device but also by other noises coming from the outside. Such the noises lead to impairment in detection sensitivity for a touch operation.
Patent Literature 1 describes a touch panel system (coordinates input device) including a countermeasure against such noises. The touch panel system of Patent Literature 1 includes a noise processing section for removing a noise. FIG. 19 is a block diagram illustrating a noise processing section 100 included in the touch panel system of Patent Literature 1. As shown in FIG. 19, the noise processing section 100 includes a filter section 101, a logical inversion section 102, and an adding section 103. The filter section 101 receives an output signal (analog signal) from a sensor provided in a touch panel (not illustrated). The filter section 101 extracts, as a noise signal, an AC signal component included in the input signal. The logical inversion section 102 inverts by 180° the phase of the noise signal thus extracted. The adding section 103 adds, to the input signal which is supplied to the filter section 101 and which includes the noise signal, the noise signal whose phase has been inverted by 180°.
Thus, according to the touch panel system of Patent Literature 1, the noise signal extracted by the filter section 101 is inverted, and the signal thus inverted is added to the input signal (analog signal) supplied from the sensor. Namely, to the noise component included in the input signal supplied from the sensor, such a signal is added which has the same level as the noise component and whose phase has been inverted. This cancels the noise superimposed on the input signal supplied from the sensor. This makes it possible to reduce effects given by the noise included in the input signal supplied from the sensor.
On the other hand, the description below deals with an arrangement of vertical electrodes and horizontal electrodes in a conventional capacitive touch sensor panel. FIG. 55 is a diagram illustrating an arrangement of vertical electrodes 91 and horizontal electrodes 92 in a conventional capacitive touch sensor panel. FIG. 55 corresponds to FIG. 3 of Patent Literature 2.
This conventional capacitive touch sensor panel disclosed in Patent Literature 2 includes (i) a plurality of vertical electrodes 91 provided on a vertical electrode surface and arranged at predetermined intervals in a horizontal direction and (ii) a plurality of horizontal electrodes 92 provided on a horizontal electrode surface, which is parallel to the vertical electrode surface, and arranged at predetermined intervals in a vertical direction.
Each vertical electrode 91 includes a sequence of a repeat of diamond-shaped quadrangular sections 93 and 94 connected to each other in the vertical direction. Each horizontal electrode 92 includes a sequence of a repeat of diamond-shaped quadrangular sections 95 and 96 connected to each other in the horizontal direction.
The vertical electrodes 91 and the horizontal electrodes 92, each including diamond-shaped sections, are so provided that the vertical electrodes 91 cross the horizontal electrodes 92 to constitute a capacitive touch sensor panel. In the case where such a capacitive touch sensor panel is to be placed on a display device for use, the vertical electrodes 91 and the horizontal electrodes 92 are normally each formed of transparent conductive film made of, for example, ITO (indium tin oxide). Recent years have also witnessed research on the use of graphene as a substitute for ITO.
In the case where the diamond-shaped sections as illustrated in FIG. 55 are made of, for example, ITO and arranged on a plane, each diamond-shaped section, having both center-line symmetry and center-point symmetry, exhibits a similarly symmetric capacitance change when touched by an object, such as a pen, that has a small touch area. Utilizing this symmetry in a capacitance change allows a symmetric position correction to be carried out during a touch-position detection, and thus increases the position detection precision.
FIG. 56 is a diagram illustrating an arrangement of vertical electrodes 81 and horizontal electrodes 82 in another conventional capacitive touch sensor panel, which is disclosed in Patent Literature 3. Both the vertical electrodes 81 and the horizontal electrodes 82 are arranged at predetermined intervals. The vertical electrodes 81 extend in a direction orthogonal to the direction in which the horizontal electrodes 82 extend. The vertical electrodes 81 and the horizontal electrodes 82 are arranged in the shape of a grid. The vertical electrodes 81 and horizontal electrodes 82 themselves individually include fine wires, which form a mesh.
(a) of FIG. 57 is a diagram illustrating an arrangement of vertical electrodes 71 in yet another conventional capacitive touch sensor panel, which is disclosed in Patent Literature 4. (b) of FIG. 57 is a diagram illustrating an arrangement of horizontal electrodes 72 in that capacitive touch sensor panel.
(a) of FIG. 57 illustrates an array of vertical electrodes 71 each including sections that each have a shape similar to a diamond shape and that are connected to one another in a vertical direction. (b) of FIG. 57 similarly illustrates an array of horizontal electrodes 72 each including sections that each have a shape similar to a diamond shape and that are connected to one another in a horizontal direction.
(a) of FIG. 59 is a diagram illustrating an arrangement of vertical electrodes in still another conventional capacitive touch sensor panel, which is disclosed in Patent Literature 5. (b) of FIG. 59 is a diagram illustrating an arrangement of horizontal electrodes in that capacitive touch sensor panel.
The capacitive touch sensor panel disclosed in Patent Literature 5 is a capacitance-type touch panel switch including (i) an electrically conductive X pattern group 161 including a plurality of conductive X sequences 162 arranged at slight intervals in the X direction and (ii) an electrically conductive Y pattern group 166 including a plurality of conductive Y sequences 167 arranged at slight intervals in the Y direction.
Each conductive X sequence 162 includes (i) a plurality of conductive X pads 163 that each have a substantially rhombic outline and that are arranged in the Y-axis direction and (ii) conductive X pads 163a that each have a substantially isosceles-triangular outline and that are arranged in the Y-axis direction to sandwich the conductive X pads 163. Adjacent conductive X pads 163 and 163 are connected to each other by a conductive X line 164, while adjacent conductive X pads 163 and 163a are also connected to each other by a conductive X line 164.
The conductive X pads 163 and 163a each include a mesh of (i) fine wires extending in the X direction and (ii) fine wires extending in the Y direction. Each conductive X line 164 is thin and includes three straight lines 165 extending in the Y direction and arranged at predetermined intervals in the X direction.
Each conductive Y sequence 167 includes (i) a plurality of conductive Y pads 168 that each have a substantially rhombic outline and that are arranged in the X-axis direction and (ii) conductive Y pads 168a that each have a substantially isosceles-triangular outline and that are arranged in the X-axis direction to sandwich the conductive Y pads 168. Adjacent conductive Y pads 168 and 168 are connected to each other by a conductive Y line 169, while adjacent conductive Y pads 168 and 168a are also connected to each other by a conductive Y line 169.
The conductive Y pads 168 and 168a each include a mesh of (i) fine wires extending in the X direction and (ii) fine wires extending in the Y direction. Each conductive Y line 169 is thin and includes three straight lines 160 extending in the X direction and arranged at predetermined intervals in the Y direction.
The X pattern group 161 and Y pattern group 166 arranged as above are so placed on top of each other as to extend orthogonally to each other in a planer view. The conductive X lines 164 of the conductive X sequences 162 and the conductive Y lines 169 of the conductive Y sequences 167 are stacked on top of each other to form a light-transmitting region having a light-transmitting property substantially identical to that of the conductive X pads 163 and the conductive Y pads 168.